According to Licensed Clinical Psychologist William Connor, SAD is a form of depression that is triggered by certain seasons, primarily winter.

Connor said the warning signs for SAD include low energy, less interest in getting out, trouble sleeping and irritability.

Fortunately, there are several things you can do to avoid falling into a winter depression.

Connor suggests going outside for a nice walk, hitting the gym to release endorphins, and socializing.

He also said, from a psychological viewpoint, positive behavior change can lead to positive attitude change.

"If you sit back to wait and feel like going out and doing something fun, you might end up waiting all winter and not doing it," he said. "So you need to go ahead and force yourself to do things, to be more active, to try out some new experiences, even if you don't feel like doing it at first. Don't let yourself sink into a depression that can get more and more difficult to get yourself out of."

Other tips include going on vacation or even planning a vacation to have something to look forward to.

Connor admits that some people may be skeptical of SAD, using it as an excuse to not be active.

But, he said it does exist. It's important to note, however, that it can affect people differently.